mechanics

Phases

phases

Phases the basics Phases: This section has become a disaster of epic proportions. gas & chaos have related etymology Jan van Helmont (1577–1644) Belgium Notes from some long forgotten source. “Chaos (χαος) was used to define the most disperse and fluid state of matter, that in which no particular order could be observed. Interestingly enough, when van Helmont wanted to refer to ...

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Kinetic-Molecular Theory

Kinetic-Molecular Theory

Kinetic-Molecular Theory postulates Kinetic-Molecular Theory: The postulates of kinetic–molecular theory (also known as molecular–kinetic theory) start very sensibly with… Molecules …and… Moving Which can be expanded to… Matter be molecules …and… Molecules be moving Then we need another postulate to explain what molecules are… Molecules be small …and how they behave… Molecules be elastic If you think it sounds like ...

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Gas Laws

Gas Laws

Gas Laws introduction Gas Laws: The gas laws are a set of intuitively obvious statements to most everyone in the Western world today. It’s hard to believe that there was ever a time when they weren’t understood. And yet someone had to notice these relationships and write them down. For this reason, many students are taught the three most important ...

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The Atomic Nature Of Matter

The Atomic Nature Of Matter

The Atomic Nature Of Matter atoms do exist The Atomic Nature Of Matter : What belongs in this section? Just chemistry? Or chemistry and physics? chemistry democritus philosophy, not science everything has to have an ultimate thing? chemical elements Earth, Water, Air, Fire, quintessence (aether) yellow bile (fire), black bile (earth), blood (air), and phlegm (water) Fire, Earth, Metal, Water, ...

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Thermal Expansion

thermal expansion examples

Thermal Expansion Solids Thermal Expansion: For many solids, expansion is directly proportional to temperature change. Δℓ = αℓ0ΔT Areas expand twice as much as lengths do. ΔA = 2αA0ΔT Volumes expand three times as much as lengths do. ΔV = 3αV0ΔT applications buckling expansion gap/joint anti-scalding valve bimetallic strip, thermostat expansion of holes (mounting train tires) “What’s more, the aircraft expands by 15-25 centimeters during flight ...

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Temperature

temperature

Temperature theoretical definition Temperature: One has to be careful when defining temperature not to confuse it with heat. Heat is a form of energy. Temperature is something different. We could begin with a technical definition, but I would prefer to start with a question. How hot is it? The answer to this question (or a question like this) is a ...

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Flow Regimes

Flow Regimes

Flow Regimes Reynolds number Flow Regimes: The Reynolds number (Re) is the ratio of inertial resistance to viscous resistance for a flowing fluid. It is named after the British physicist and engineer Osborne Reynolds who is generally regarded as the first to realize its importance in 1883. Re = inertial resistance  = ρvℓ viscous resistance η where… Re = Reynolds number ρ = density of the fluid v = ...

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Aerodynamic Drag

Aerodynamic Drag

Aerodynamic Drag pressure drag Aerodynamic Drag: The force on an object that resists its motion through a fluid is called drag. When the fluid is a gas like air, it is called aerodynamic drag or air resistance. When the fluid is a liquid like water it is called hydrodynamic drag, but never “water resistance”. Fluids are characterized by their ability to flow. In somewhat technical language, a fluid is ...

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Viscosity

Viscosity

Viscosity Viscosity: Informally, viscosity is the quantity that describes a fluid’s resistance to flow. Fluids resist the relative motion of immersed objects through them as well as to the motion of layers with differing velocities within them. Formally, viscosity (represented by the symbol η “eta”) is the ratio of the shearing stress (F/A) to the velocity gradient (Δvx/Δz or dvx/dz) in a fluid. η = F̅/A Δvx/Δz or η = F/A dvx/dz ...

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Fluid Flow

Fluid Flow

Fluid Flow Fluid Flow: continuity equation For incompressible fluid flow… φ = V  = Av = constant  ⇒ A1v1 = A2v2 t If the fluid is compressible, then… I = m  = ρAv = constant  ⇒ ρ1A1v1 = ρ2A2v2 t Fluid Flow: Notes from The Economist — “A sverdrup (named for the Norwegian oceanographer and meteorologist Harald Sverdrup) the unit in which ocean currents are measured, is one million cubic metres of ...

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